What is turbulence?
There are three main types of turbulence that matter for aviation. One is generated by mountain ranges such as the Andes and the Rockies.
The second is clear air turbulence, the main issue for commercial airline pilots. It is typically caused by jet streams, the “rivers” of air that flow from the west to the east in the mid-latitudes. Planes use these jet streams to fly faster from the US to the UK but they also generate pockets of turbulence which, as the name suggests, are invisible.
Finally, there is convective turbulence, when hot air rises because of warmth in the land or sea. Mark Prosser, a PhD researcher at the University of Reading, speculated that the death on the London to Singapore flight could be linked to convective turbulence, as the Bay of Bengal is very warm.
How is turbulence monitored?
Mostly by aircraft acting as an early warning system for one another. Pilots who hit a patch of turbulence make an instantaneous report and control centres relay that information to other pilots.
Some planes are equipped with accelerometers to measure the turbulence. Turbulence is also forecast across the world. According to Paul Williams, also a professor at the University of Reading, forecasts in the past were about 60 per cent accurate — but that has increased to about 80 per cent now.
Advertisement
“But you still get false positives, where we say we think there will be turbulence there and it turns out there wasn’t; and you still get false negatives, where you say that area should be OK and it isn’t,” Prosser said.
How common is turbulence?
At the cruising altitude at which commercial planes fly, just 0.1 per cent of the world at any given time is affected by severe levels of turbulence, of the kind that could lift you off the floor. Even with severe turbulence, however, passengers should typically be OK if they are wearing seatbelts.
• Is turbulence dangerous? How to stay calm on a bumpy flight
“What happened to that plane was probably extreme, much rarer than severe turbulence,” Prosser said.
By comparison, just 0.4 per cent of the atmosphere where planes fly is affected by moderate turbulence. The figure rises to 3 per cent for light turbulence.
Advertisement
How has turbulence changed over time?
Severe turbulence over the north Atlantic increased by 55 per cent, rising from 17.7 hours in 1979 to 27.4 hours in 2020, according to a paper published by Williams, Prosser and colleagues last year. The researchers blamed climate change for the increase in turbulence.
How bad can turbulence get?
When turbulence is classified as severe, it means that people experience a force of at least 1G when a plane falls. “If you’re not strapped in you will lift off over 1G, and that’s not safe at all,” Prosser said.
How common are deaths from turbulence?
Although deaths because of turbulence do happen occasionally in small planes, they are vanishingly rare in commercial flights such as the Singapore Airlines one in which a British man died from a suspected heart attack. The last time someone died from unexplained turbulence was in 2009, and the last death known to have been from clear-air turbulence was in 1997, Prosser said.
What can airlines do?
Improving the accuracy of forecasting would help hugely, Prosser said. For now, though, the best bet is to keep wearing your seatbelt, regardless of what the plane’s lights say.
